Human-Powered Helicopter Attempts Prize-Winning Flight Today

University of Maryland student Brandon Draper prepares for a flight yesterday. Photo: University of Maryland/A. James Clark School of Engineering

Students from the University of Maryland hope to keep a human-powered helicopter aloft for at least one minute today and win one of the most elusive prizes in aviation.

The 71-pound Gamera II is powered by a combination of hand and foot pedaling by a single pilot, who must keep the four-rotor helicopter aloft for 60 seconds and reach an altitude of at least 3 meters (9.8 feet) to win the $250,000 Sikorsky Human-Powered Helicopter prize. The team already holds the record for the longest human-powered flight, at 65 seconds, and the highest altitude, at 9 feet, following a remarkable flight last summer but so far has not met all of the requirements of the Sikorsky prize in a single flight.

That could change today when the team attempts another flight. They can be followed on their Twitter feed here.

The 51 undergraduate and graduate students working on the project spent Wednesday preparing and testing Gamera II for a record attempt. With officials of the National Aeronautic Association present to inspect the aircraft and witness the flights, Gamera II made a series of warm-up and tuning flights of 30 to 40 seconds. Some structural sections of the delicate aircraft broke during the day, and the team spend much of the night making repairs.

To claim the $250,000 prize, the pilot (which is, of course, also the engine) must keep the helicopter within a 10-square-meter box (108 square feet) in addition to the time and height requirements. Like all of the other recent human-powered helicopters, the University of Maryland students are flying their 105-foot, 71-pound quad-copter indoors to reduce the chance of wind affecting the flight. But even with the still air of a large indoor space, there are plenty of challenges to overcome. The slightest asymmetry generated by the 42.6-foot rotors will cause the helicopter to deviate from a vertical hover.

Another challenge has been keeping the helicopter together. At just 71 pounds, Gamera II is, to be blunt, not a strong aircraft. An incredibly intricate design of small carbon-fiber tubes form small trusses that are linked to create larger trusses that connect the four rotors to the “cockpit.” The pilot uses his arms and legs to turn a pair of gears that drive the rotors. A video from a flight last year shows how the slow-spinning rotors get the helicopter airborne, but also how delicate the structure is after breaking due to some lateral drift during the landing.

Gamera II places the delicate mylar-covered blades beneath the main structure of the helicopter, as close to the ground as possible. The advantage of this design is an interesting aerodynamic phenomenon known as ground effect. This reduces some of the drag associated with lift, so less power is needed to achieve flight. The same effect allows conventional helicopters to hover at higher altitudes or with heavier loads in ground effect compared to when they are “out of ground effect.”

The rotor blades feature changing airfoils from the root to the tip as well as a tapered profile to reduce tip deflection at full power. Several scientific papers have been written during the Gamera program, including a careful analysis of the rotor design (.pdf).

The University of Maryland team isn’t alone in pursuing the Sikorsky prize. A group of Canadians in Ontario made an attempt earlier this month with their Atlas helicopter. The Canadian team has experience making human-powered aircraft having produced an ornithopter which made its first flight in 2009. After a snowstorm canceled soccer games at the facility where the Canadians were flying, they hoped to use the extra field time to make a serious run at the prize. But an unfortunate out-of-balance rotor led to a structural failure of a spar, ending the flights before a significant attempt could be completed.

The University of Maryland team prepares Gamera II for a prize winning flight. Photo: University of Maryland/A. James Clark School of Engineering

Gamera’s longest flight yet, achieved last summer, shows what a human-powered helicopter looks like in flight.